1. Field of the Invention
The present invention relates to a flexible flat cable, and particularly to a flexible flat cable manufactured through extrusion.
2. Description of the Related Art
A flexible flat cable is used to electrically connect, for example, a moving portion and a fixed portion due to its flexibility, is very flexible in terms of shape, only requires a small space, and can be easily wound as necessary. Due to the above advantages, a flexible flat cable has an extremely wide range of uses such as the connection between a scanner head, a printer head, or the like and a main body portion which is a fixed portion, and a clock spring in an automobile.
Such a flexible flat cable was frequently manufactured using a lamination method. Such a method includes the technique proposed in JP-A-10-278206. That is, the technique is to laminate a conductor using a composite sheet which is manufactured by laminating a heat seal layer composed of a heat seal resin on a base material sheet composed of a saturated polyester resin imparted with fire retardance.
Here, high sliding curvature characteristics that a flexible flat cable needs to have were obtained from the heat seal layer, and sufficient adhesion properties to a conductor was secured.
However, the above method has a number of processes such as a base material sheet manufacturing process, a heat seal layer forming process, and a lamination process, the manufacturing costs become extremely high compared to, for example, a coated wire manufactured through ordinary extrusion, and, while having been used as a component that requires extremely high curvature resistance (for example, ten million times or more) such as a clock spring in the automobile field, the flexible flat cable has rarely been applied to doors such as a slide door whose thickness and size can be decreased through use of the flexible flat cable.
Here, International Publication WO2008/056772 (Patent Document 1) proposes a technique in which a flexible flat cable is manufactured using a thermoplastic resin having a curvature elastic modulus of equal to or more than 200 MPa to less than 800 MPa through extrusion. According to the technique, a flexible flat cable that is excellent in terms of sliding curvature resistance can be obtained.
However, in a case in which the above thermoplastic resin is used, there was a problem in that it is not possible to coat a conductor with the resin when a thin flexible flat cable is manufactured, or a uniform structure cannot be obtained.
Particularly, in the past, it was not possible to manufacture a thin flexible flat cable having an insulating layer with a thickness of 0.2 mm or less on a conductor which is required for the use of, for example, a narrow cable routing space for automobiles such as appliance cable routing.